TOP242-250

M

12/04

2

Section List

Functional Block Diagram ....................................................................................................................................... 3

Pin Functional Description ...................................................................................................................................... 4

TOPSwitch-GX

Family Functional Description ....................................................................................................... 5

CONTROL (C) Pin Operation.................................................................................................................................. 6

Oscillator and Switching Frequency........................................................................................................................ 6

Pulse Width Modulator and Maximum Duty Cycle.................................................................................................. 7

Light Load Frequency Reduction............................................................................................................................ 7

Error Amplifier ......................................................................................................................................................... 7

On-Chip Current Limit with External Programmability ............................................................................................ 7

Line Under-Voltage Detection (UV)......................................................................................................................... 8

Line Overvoltage Shutdown (OV) ........................................................................................................................... 8

Line Feed-Forward with DC

Remote ON/OFF and Synchronization ................................................................................................................... 9

Soft-Start................................................................................................................................................................. 9

Shutdown/Auto-Restart........................................................................................................................................... 9

Hysteretic Over-Temperature Protection................................................................................................................. 9

Bandgap Reference.............................................................................................................................................. 10

High-Voltage Bias Current Source........................................................................................................................ 10

Using Feature Pins ................................................................................................................................................... 10

FREQUENCY (F) Pin Operation........................................................................................................................... 10

LINE-SENSE (L) Pin Operation ............................................................................................................................ 10

EXTERNAL CURRENT LIMIT (X) Pin Operation.................................................................................................. 11

MULTI-FUNCTION (M) Pin Operation .................................................................................................................. 11

Typical Uses of FREQUENCY (F) Pin ...................................................................................................................... 14

Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins ...................................................... 15

Typical Uses of MULTI-FUNCTION (M) Pin ........................................................................................................... 17

Application Examples .............................................................................................................................................. 20

A High Efficiency, 30 W, Universal Input Power Supply........................................................................................ 20

A High Efficiency, Enclosed, 70 W, Universal Adapter Supply.............................................................................. 20

A High Efficiency, 250 W, 250-380 VDC Input Power Supply ............................................................................... 22

Multiple Output, 60 W, 185-265 VAC Input Power Supply .................................................................................... 23

Processor Controlled Supply Turn On/Off............................................................................................................. 24

Key Application Considerations ............................................................................................................................. 26

TOPSwitch-II vs. TOPSwitch-GX.......................................................................................................................... 26

TOPSwitch-FX vs. TOPSwitch-GX ....................................................................................................................... 28

TOPSwitch-GX Design Considerations ............................................................................................................... 28

TOPSwitch-GX Layout Considerations................................................................................................................. 30

Quick Design Checklist......................................................................................................................................... 32

Design Tools ......................................................................................................................................................... 32

Product Specifications and Test Conditions ......................................................................................................... 33

Typical Performance Characteristics .................................................................................................................... 40

Part Ordering Information ....................................................................................................................................... 46

Package Outlines ..................................................................................................................................................... 47